Cooling system



June 20, 1961 Filed Dec. 21, 1959 J. A. LAUCK COOLING SYSTEM 2 Sheets-Sheet 1 INVENTOR.

JOHN A. LAUCK ATTORNEY.

J. A. LAUCK COOLING SYSTEM June 20, 1961 2 Sheets-Sheet 2 FIG. 3

Filed Dec. 21, 1959 FIG. 5

INVENTOR.

JOHN A. LAUCK QKW ATTORNEY.

United States Patent 2,988,888 COOLING SYSTEM John A. Lauck, Benton Harbor, Mich., assignor to Clark Equipment Company, a corporation of Michigan Filed Dec. 21, 1959, Ser. No. 860,994 10 Claims. (CI. 60-52) The present invention relates to a cooling system, and more particularly to a cooling system for reservoirs in hydraulic systems and the like.

In conventional hydraulic systems, one or more cylinders are operated by fluid supplied from a reservoir by a positive displacement pump and controlled by a valve which admits fluid from the pump to one end or the other of the operating cylinder at the will of the operator, and returns the fluid from the pump to the reservoir during the time when the cylinders are not being operated. In many installations, particularly in those systems incorporated in earth moving equipment, tractors and similar vehicles operated over long periods of time in hot weather, the fluid in the hydraulic system becomes hot, sometimes being raised to a temperature sufliciently high to damage the pumps, valves and cylinders in the hydraulic system, resulting in excessive servicing and frequent replacement of parts. It is, therefore, one of the principal objects of the present invention to provide an efi'icient and relatively simple and compact cooling system for hydraulic systems of the aforementioned type which utilizes the fluid returning from the pump to the reservoir, particularly during the time the pump pressure is not being used to perform other operations.

Another object of the invention is to provide a cooling system for the reservoirs of hydraulic systems and the like which does not increase the operating cost of the hydraulic system and which can readily be installed either as original equipment or as an accessory in the field, without any substantial changes being required in the structure comprising the hydraulic system andwithout an appreciable increase in cost of the complete system.

Still another object of the invention is to provide a cooling system for a conventional hydraulic system, which is operated and controlled by the pump and control valve of the hydraulic system without interfering with or varying the operation of the hydraulic system.

Further objects and advantages of the invention will become apparent from the following description and accompanying drawings, wherein:

FIGURE 1 is a schematic view of a hydraulic system having incorporated therein one embodiment of the present cooling system, the reservoir, pump, control valve and operating cylinder being shown in vertical crosssection;

FIGURE 2 is a vertical cross-sectional view of a hydraulic fluid reservoir showing a modified form of my reservoir cooling system;

FIGURE 3 is a side elevational view of the hydraulic fluid reservoir shown in FIGURE 2. with the external shell removed and with one type of motor suitable for use in the present cooling system being shown in vertical cross-section;

FIGURE 4 is a vertical cross-sectional view of a hydraulic fluid reservoir showing a further modified form of my reservoir cooling system; and

FIGURE 5 is a side elevational view of the hydraulic fluid reservoir shown in FIGURE 4 with the external shell removed and with a vertical cross-sectional view through another type of motor suitable for use in the present cooling system being shown in vertical crosssection.

Referring more specifically to the drawings and to FIGURE 1 wherein a complete hydraulic system is shown diagrammatically, numeral designates a hydraulic 2,988,888 Patented June 20, 1961 fluid reservoir, 12 a gear pump, 14 a control valve, and 18 an operating cylinder, and numeral 20 designates generally my cooling system for the reservoir 10. Pump 12, which is a conventional gear type, is connected to the reservoir by an inlet conduit 22 and to control valve 14 by an outlet conduit 24, and consists of housing 26 having a chamber 28 in which two intermeshing gears 30 and 32 are rotatably mounted on shafts 34 and 36, respectively. The gears are driven through one of the shafts by a suitable power source, for example an electric motor or a shaft from the engine of a vehicle in which the hydraulic system is incorporated.

Control valve 14, which for the purpose of the present description may be considered as a conventional spool valve, consists of a body 38 having a chamber 40, an inlet passage 42 connected to conduit 24, and five outlet passages 44, 46, 48, 50 and 52 controlled by a spool valve element 54 in chamber 40. Passages 44 and 46 are connected to opposite sides of a piston 56 in cylinder 18 by conduits 58 and 60, respectively, and the movement of the piston in response to fluid supplied through the latter conduits transmitted to a mechanism (not shown) operated in the present hydraulic system by rod 62 and a suitable connecting linkage. Passage 43 is connected to reservoir 10 by a conduit 64 which returns the fluid from pump 12 to the reservoir during the operation of the system while the hydraulic cylinder is inoper able. Passage 50 is connected to the reservoir by conduits 66, 67 and 64, and passage 52 is connected to the reservoir by conduits 68, 67 and 64, which return the fluid to the reservoir from cylinder 18 on opposite sides of piston 56. Spool valve element 54 is operated by a pivoted lever 70 and contains two centrally located lands 74 and 76 controlling the return of fluid from the pump through passage 48 and conduit 64 directly to the reservoir, and lands 78 and 80 controlling passages 44 and 46, respectively, for regulating the flow of fluid from chamber 40 into cylinder 18 and from the cylinder through conduits 66 or 68 and thence through conduits 67 and 64 to the reservoir. Lands 82 and 84 at opposite ends of the valve element are provided for sealing the ends of chamber 40.

The cooling system 20 consists of a fan or blower driven by a hydraulic motor 92 for circulating air through the space 94 between the external surface of the side and bottom Walls of reservoir 10 and a sheet metal shell 96 spaced from and paralleling the corresponding walls of the reservoir. In the particular embodiment shown in FIGURE 1, the air is drawn into space 94 through opening 98 in the bottom'wall and is discharged at the top of the side walls, and the fan is mounted in the space between the reservoir and the shell adjacent opening 98. The particular type of fan or blower employed in the system is not considered important to the present invention, the one shown consisting of a plurality of radial blades forming an impeller which draws air inwardly near the center and discharges it at the periphery of the blades throughout its circumference. An annular bafile 99 disposed near the periphery of the impeller assists in directing and distributing the air discharged by the fan through the space between the reservoir and shell 96.

Various types of hydraulic motors may be used to drive the fan, the motor 92 shown in FIGURE 1 being a gear type of well-known construction located at the bottom of the reservoir and connected to the fan by a shaft 100 extending downwardly from the motor through the bottom Wall of the reservoir. The vertical cross-sectional view of the motor shows the housing 101 having inletand outlet passages 102 and 104 and gears 106 and 108,-

the cross-section being taken on a line intersecting the intermeshing portion of the gears. Motor 92 which-is completely immersed in the hydraulic fluid in the reservoir '3 23 discharges through outlet passage 104 directly into the reservoir and receives operating fluid from pump 12 through conduit 22 and valve 14 by conduit 64 while cylinder 18 is inoperative, and by either conduits 66 or 68 when the cylinder is being operated. The motor is driven continually by the fluid discharged from the pump either directly through the valve as long as element 54 is in its neutral position, or indirectly through the valve from cylinder 18 while element 54 is in its right or left positions. In the normal operation of most hydraulic systerns, the pump is driven continually, and consequently provides a dependable and constant source of fluid pressure for operating the hydraulic motor. Since the type of motor shown obstructs the flow of fluid from conduit 64 when the gears are not rotating, a by-pass or safety valve 110 is included in conduit 64 Within the portion in the reservoir to permit the fluid to discharge from the conduit in the event the gears of the motor fail to rotate in response to a build-up of fluid pressure in conduit 64. This adverse condition would most likely be created by a foreign object contacting the fan and preventing rotation, or foreign particles becoming wedged between the motor gear or gears and internal walls of the housing. The by-pass valve 110 is a pressure-relief type valve of well-known construction and operation and will not be described in detail herein. In some installations it may be desirable to utilize only the fluid returning to the reservoir while the valve is in neutral position to drive the motor.

In the operation of the system just described, starting with a full supply of fluid, the pump is started and operated continuously as long as the vehicle is in use or as long as there is likely to be a demand on the system. With the valve in the neutral position shown in FIGURE 1, fluid from the pump passes through conduit 24, valve chamber 40, passage 48 and conduit 64 to motor 92 which continues to operate and drive fan 90 as long as the valve is maintained in its neutral position. When the hydraulic cylinder is to be operated, for example in the direction to retract rod 62, spool valve element 54 is moved to the left by the operator using lever 70, thus connecting conduit 58 and the cylinder on the left hand side of piston 56 with the high fluid pressure in chamber 40, and simultaneously interrupting the flow of fluid directly through conduit 64 to motor 92. With the valve element in this position the motor is driven by the fluid returning to the reservoir through conduits 60, 68, 67 and 64 from the right hand side of piston 56. Upon the movement of piston 56 to the left to the desired position, the operator returns the valve element to the neutral position, again permitting the discharge from the pump to pass directly through conduit 64 to the motor. Since operation of the hydraulic cylinder is normally for only short intervals with the valve remaining in its neutral position at all other times, motor 92 and the fan 90 are driven most of the time by the output of the pump not otherwise being utilized.

In the modified form of the present invention disclosed in FIGURES 2 and 3, the motor 120 is mounted on the side of the reservoir and consists of an impeller 122 of the Pelton wheel type mounted on a shaft 124 and driven by fluid from pump 12 discharged from a nozzle 125 onto blades 126 of the impeller. The impeller is enclosed in a housing 127 attached to the side of the reservoir and connected to the interior of the reservoir through an opening 128 near the bottom of the housing. Shaft 124 is journalled in bearings 130 and 132 seated in recesses in the adjacent side walls of the reservoir and housing and is provided with an extension 134 projecting outwardly through the housing wall for receiving a fan 136. A shell 138 surrounds the side walls and bottom of the reservoir and is spaced therefrom to provide a passage for circulating air. and contains an enlarged portion for enclosing the hydraulic motor and fan. The air enters the space between the reservoir and shell through an opening 140 and is discharged along the open top of the shell. Thehydraulic 4- system including the control valve may be the same in the modified form of FIGURES 2 and 3 as the system shows in FIGURE 1.

The further modified form of the invention shown in FIGURES 4 and 5 is similar in most respects to the form disclosed in FIGURES 2 and 3; however, in this modification the motor housing is adapted to be secured to the flange 152 of the standard clean-out opening 154 of the reservoir. The housing is secured to flange 152 by a plurality of bolts 158 extending through an annular flange 160 on the base of the housing. The impeller 162, consisting of a number of paddle wheel blades 164, is mounted in the motor housing on a shaft 166 which extends through one wall of the housing and receives fan 168. The shaft is journalled in bearings 170 and 172 seated in recesses in the side walls of the housing. Fluid under pressure from pump 12 is discharged through a nozzle 174 onto blades 164 and thereafter returns to the reservoir through opening 154. Air is drawn through an opening 176 in the side of shell 178 which encloses the side walls and bottom of the reservoir andmotor housing and is directed through the space 180 between the reservoir and shell and discharged at the opening 182 at the top of the shell.

While only three embodiments of my cooling system have been shown in detail herein, various changes and other modifications may be made without departing from the scope of the invention. For example, various other types of hydraulic motors and fans driven thereby may be used in place of those shown in the drawings and the motor and fan may be located at other places on or relative to the reservoir. Further, other types of heat exchangers may be substituted for the shell structures shown.

I claim:

1. In combination with a hydraulic system having a reservoir, a gear pump, a conduit connecting the reservoir with said pump, a hydraulic cylinder having a piston therein, a spool valve having a neutral position and two operating positions, a conduit connecting said pump with said valve, and conduits connecting said valve with said cylinder on opposite sides of said piston; a cooling system for said hydraulic system including a shell surrounding a portion of said reservoir having an air inlet opening and an air outlet opening and :being spaced from said reservoir to form an air passage, a fan in said air passage adjacent said inlet opening, a gear type hydraulic motor disposed in the bottom of said reservoir, a shaft connecting said motor with said fan, a conduit connecting said valve with said motor in said reservoir for returning fluid to the reservoir when the valve is in its neutral position and in either of its two operating positions, said last mentioned conduit having a section extending through said reservoir, and a relief valve in said conduit section.

2. In combination with a hydraulic system having a reservoir, a gear pump, a conduit connecting the reservoir with said pump, a means operated by fluid under pressure from the pump, a valve having a neutral position and two operating positions, a conduit connecting said pump with said valve, and a conduit connecting said valve with the fluid operated means; a cooling system for said hydraulic system including a shell surrounding a portion of said reservoir having an air inlet opening and an air outlet opening and being spaced from said reservoir to form an air passage, a fan in saidair passage, a hydraulic motor, a shaft connecting said motor with said fan disposed in the bottom of said reservoir, a conduit connecting said valve with said motor for returning fluid to said reservoir when the valve is in its neutral position and in either of its two operating positions, and a relief valve in said last mentioned conduit.

3. Incombination with a hydraulic system having a reservoir, a positive displacement pump, a conduit connecting the reservoir with said pump, a means operated by fluid under pressure from the pump, a valve having a neutral position, a conduit connecting said pump with said valve, and a conduit connecting said valve with the fluid operated means; a cooling system for said reservoir including a shell surrounding a portion of said reservoir having an air inlet opening and an air outlet opening and being spaced from said reservoir to form an air passage, a fan in said air passage adjacent said inlet opening, a gear type hydraulic motor for driving said fan, and a conduit connecting said valve with said motor for driving said motor and returning fluid to said reservoir when the valve is in its neutral position.

4. In combination with a hydraulic system having a reservoir, a gear pump, a conduit connecting the reservoir with said pump, a means operated by the fluid under pressure from the pump, a valve having a neutral position and two operating positions, a conduit connecting said pump with said valve, and a conduit connecting said valve with the fluid operated means; a cooling system for said reservoir including a shell surrounding a portion of said reservoir having an air inlet opening and an air outlet opening and being spaced from said reservoir to form an air passage, a fan in said air passage, a hydraulic motor for driving said fan, and a conduit connecting said valve with said motor for driving said motor and returning fluid to said reservoir when the valve is in its neutral position and in either of its two operating positions.

5. In combination with a hydraulic system having a reservoir, a pump, a conduit connecting the reservoir with said pump, a means operated by the fluid under pressure from the pump, a valve having a neutral position, a conduit connecting said pump with said valve, and a conduit connecting said valve with fluid operated means; a cooling system for said reservoir including a shell surrounding a portion of said reservoir having an air inlet opening and an outlet opening and being spaced from said reservoir to form an air passage, a fan in said air passage adjacent said inlet opening, a hydraulic motor having an impeller with blades, a nozzle for discharging fluid onto said impeller blades, a housing for said impeller mounted on the side of said reservoir and connected by an opening to the interior of said reservoir, a shaft connecting said impeller motor with said fan, and a conduit connecting said valve with said nozzle when the valve is in its neutral position.

6. In combination with a hydraulic system having a reservoir, a pump, a conduit connecting the reservoir with said pump, a means operated by the fluid under pressure from the pump, a valve having a neutral position, a conduit connecting said pump with said valve, and a conduit connecting said valve with fluid operated means; a

cooling system for said reservoir including a shell surrounding a portion of said reservoir having an air inlet opening and an air outlet opening and being spaced from said reservoir to forman air passage, a fan in said air passage, a hydraulic motor having an impeller with blades, a nozzle for discharging fluid onto said impeller blades, and a conduit connecting said valve with said nozzle when the valve is in its neutral position.

7. The cooling system defined in claim 6 wherein the blades on the impeller are cup-shaped.

8. The cooling system defined in claim 6 wherein the blades on the impeller are paddle-shaped.

9. In combination with a hydraulic system having a reservoir, a pump, a conduit connecting the reservoir with said pump, a means operated by fluid under pressure from the pump, a valve having a neutral position, a conduit connecting said pump with said valve, and a conduit connecting said valve with fluid operated means; a cooling system for said reservoir including means forming a heat exchanger having an air passage with inlet and outlet openings, a fan in said air passage, a hydraulic motor for driving said fan, and a conduit connecting said valve with said motor for driving said motor and returning fluid to said reservoir when the valve is in its neutral position.

10. In combination with a hydraulic system having a reservoir, a pump, a conduit connecting the reservoir with said pump, a means operated by the fluid under pressure from the pump, a valve having a neutral position, a conduit connecting said pump with said valve, and a conduit connecting said valve with fluid operated means; a cooling system for said reservoir including means forming a heat exchanger having an air passage with inlet and outlet openings, a fan in said air passage, a hydraulic motor having an impeller with blades, a nozzle for dis charging fluid onto said blades, a housing for said impeller mounted on the side of said reservoir and connected by an opening to the interior of said reservoir, a shaft connecting said impeller motor with said fan, and a conduit connecting said valve with said nozzle.

References Cited in the file of this patent UNITED STATES PATENTS 2,035,813 Johnson Mar. 31, 1936 2,409,374 McGill Oct. 15, 1946 2,585,149 McGill Feb. 12, 1952 FOREIGN PATENTS 790,430 Great Britain Feb. 12, 1958 

